The present invention relates to a guide vane segment for a gas turbine, in particular an aircraft gas turbine, comprising at least one radially outer shroud and one radially inner shroud, which extend along a respective arc and together form an annular segment, wherein, in the radial direction between the outer shroud and the inner shroud, a plurality of guide vanes are arranged adjacent to one another in the peripheral direction and are joined to the inner shroud and to the outer shroud in a material-bonded manner and, in particular, are joined in a one-piece manner, wherein, in an axial lengthwise direction, the outer shroud comprises an axially front end wall element and an axially rear end wall element in such a way that the outer shroud and the two end walls form a tub-like profile in lengthwise section, wherein, at the axially rear end wall, at least one radial securing element is provided, which is constructed for the purpose of securing the guide vane segment in the radial direction relative to a surrounding housing, wherein the radial securing element is designed as a projection with a support section that is constructed so as to rest against a corresponding counterpiece on the housing.
In the present application, statements of direction such as “axial” or “axially,” “radial” or “radially,” and “peripheral” are to be understood fundamentally as being referred to the machine axis of the gas turbine, unless something else is to be inferred explicitly or implicitly from the context.
For an improved and simplified assembly of the guide vane segments, which can also be referred to as guide vane clusters, in a gas turbine, it has been shown that the provision of radial securing elements represent a fitting alternative to the hitherto known securing catches.
What is particularly involved in the radial securing of guide vane segments, which are generally assembled together in a gas turbine to form a guide vane ring, is to secure the guide vane segments inside the turbine housing in the radial direction so as to prevent them from dropping out. During operation of the gas turbine, a torque generally acts on the guide vane segment due to the flow to which the guide vane(s) is or are exposed, said torque being of such a nature that the axially rear end wall element is pressed radially outward, whereas the axially front end wall element is pulled radially inward. This torque is absorbed at the axially rear end wall element by resting the radially outer edge thereof against the housing. However, if the turbomachine is not in operation, then the flow in the gas duct that is acting on the guide vanes is absent. The radial securing to prevent the guide vane segments from dropping out or the radial securing element described here serves above all for this case. In this way, when the turbomachine is shut down, it is prevented that the guide vane segment will be able to drop out, for example, due to the force of gravity.
Lesser forces need to be accommodated in the radial direction during operation of the gas turbine. Accommodation of forces acting in the radial direction can then optimally occur, in general, when a support surface area has a normal vector that has only vector components in the radial direction or/and in the axial direction. However, it has been shown that such support surface areas are rather complicated to manufacture when the support area is to be curved in the peripheral direction in correspondence with the radius referred to the machine axis or when the support surface area lies in a tangential plane with respect to the periphery in the region of the outer shroud.